At present, to provide a low-profile antenna circuit, a flexible circuit substrate is laminated on both major opposing surfaces with a metallic electrically conductive layer, in this case being copper. An antenna coil for use with an RFID circuit, NFC circuit or other wireless radio-frequency communication circuit is then etched or otherwise provided on a front said major surface, and a crossover element is provided on a rear said major surface. The crossover element is a short link track or trace of copper left by the removal of the rest of the copper layer on the rear major surface.
Through holes or vias are then formed between the front and rear major surfaces, interconnecting an inner end portion of the antenna coil with a first end of the crossover element and an outer end portion of the antenna coil with a second end of the crossover element. The through holes are then plated to electrically connect the antenna coil and the crossover element, thereby forming the antenna circuit.
However, the removal of such a large amount of copper from the rear major surface causes significant waste and increases manufacturing cost. The through holes can only be formed using laser or highly accurate drilling technology, which again leads to increased manufacturing time and a potentially higher scrap rate due to drilling position inconsistencies. Furthermore, the plating of the through holes disrupts the current flow, thereby altering the resistance of the circuit and thus reducing operational performance.
The present invention seeks to provide a solution to these problems.